cranelift_codegen

Module verifier

Source
Expand description

A verifier for ensuring that functions are well formed. It verifies:

block integrity

  • All instructions reached from the block_insts iterator must belong to the block as reported by inst_block().
  • Every block must end in a terminator instruction, and no other instruction can be a terminator.
  • Every value in the block_params iterator belongs to the block as reported by value_block.

Instruction integrity

  • The instruction format must match the opcode.
  • All result values must be created for multi-valued instructions.
  • All referenced entities must exist. (Values, blocks, stack slots, …)
  • Instructions must not reference (eg. branch to) the entry block.

SSA form

  • Values must be defined by an instruction that exists and that is inserted in a block, or be an argument of an existing block.
  • Values used by an instruction must dominate the instruction.

Control flow graph and dominator tree integrity:

  • All predecessors in the CFG must be branches to the block.
  • All branches to a block must be present in the CFG.
  • A recomputed dominator tree is identical to the existing one.
  • The entry block must not be a cold block.

Type checking

  • Compare input and output values against the opcode’s type constraints. For polymorphic opcodes, determine the controlling type variable first.
  • Branches and jumps must pass arguments to destination blocks that match the expected types exactly. The number of arguments must match.
  • All blocks in a jump table must take no arguments.
  • Function calls are type checked against their signature.
  • The entry block must take arguments that match the signature of the current function.
  • All return instructions must have return value operands matching the current function signature.

Global values

  • Detect cycles in global values.
  • Detect use of ‘vmctx’ global value when no corresponding parameter is defined.

Memory types

  • Ensure that struct fields are in offset order.
  • Ensure that struct fields are completely within the overall struct size, and do not overlap.

TODO: Ad hoc checking

  • Stack slot loads and stores must be in-bounds.
  • Immediate constraints for certain opcodes, like udiv_imm v3, 0.
  • Insertlane and extractlane instructions have immediate lane numbers that must be in range for their polymorphic type.
  • Swizzle and shuffle instructions take a variable number of lane arguments. The number of arguments must match the destination type, and the lane indexes must be in range.

Structs§

Functions§

Type Aliases§